The present invention relates to a method and apparatus for applying a thin film of a liquid to a vibratory plate of a vibratory compactor. More particularly, the present invention relates to a method and apparatus that applies a thin film of liquid to the underside of an inclined plate of a compactor and maintains the film in contact with the plate until the film reaches a generally flat lower plate. The film of liquid prevents the material being compacted from sticking to the plate.
Compactors of the type having an inclined plate arranged at a forward and/or rearward edge of a flat vibratory plate are known. Such compactors are useful to pack soil or asphalt. However, particularly when the compactor is utilized with hot asphalt, the material being compacted tends to stick to the plates during operation. The material buildup necessitates periodic cessation of the compacting operation to clean the vibratory plates and allow efficient operation. Failure to clean the plates results in material buildup thereon which, in turn, causes an uneven finish to occur on the surface being compacted. Also, the additional material appreciably increases the weight of the plates and hence the moving mass increases causing an excess load on a motor driving the plates. Therefore, an economical and efficient method and apparatus are desirable to apply a liquid, preferably water, to the vibratory plates to prevent the material from sticking to the plates. The liquid prevents sticking by cooling the plate and/or by forming a liquid interface which does not mix, i.e., is immiscible, with the material being compacted.
One known apparatus which attempts to apply water to the vibratory plate of a compactor consists of an elongated tube arranged along a front surface of the inclined plate with a plurality of holes being provided along a longitudinal axis of the tube. Water is fed to a central location in the tube and dispersed through the holes along the length of the tube. However, a device of this type fails to apply a sufficient quantity of water to the bottom plate where the greatest portion of sticking occurs. Due to the violent action of the vibratory plate, the water emanating from the plurality of holes in the tube tends to be flung about in all directions. Consequently, a device of this type deposits as much water on the engine and the remainder of the compactor as is deposited where the water is needed on the plate or the material being compacted.
Another known device is used to wet a tire of a road roller to prevent material from adhering to the tire. The device includes an arcuate carrier arranged above the tire surface. Attached to a lower face of the carrier is a wiping element in the form of a coco-mat. Arranged above the coco-mat is a perforated spray pipe which directs water onto the coco-mat. However, a device of this type relies partially upon relative movement of the tire surface while in contact with the coco-mat in order to wipe the tire clean. Such a device is disclosed in U.S. Pat. No. 2,197,183 issued Apr. 16, 1940 to Keeler.
A device for distributing water to a road roller is also known that includes a vulcanized rubber mat arranged adjacent to the roller surface and connected to a holder which supports a sprinkler or spray tube. The object of the device is to prevent material from adhering to the roller surface. A device of this type also relies upon relative movement of the roller past the rubber mat to clean the surface. Such a device is disclosed in U.S. Pat. No. 4,040,762 issued Aug. 6, 1977 to Nilsson.
A free flowing water system for a roller of an asphalt rolling machine is also known. The water system is mounted adjacent to a front face of the roller and includes a water trough comprised of a vertical flange and a horizontal flange. A rubber blade provided on the base of the trough contacts the surface of the roller. In operation, water contained in the trough is dispensed to the surface of the roller by the rubber blade to prevent asphalt build-up on the roller. A device of this type as, for example, disclosed in U.S. Pat. No. 3,675,546 issued July 11, 1972 to Smith, does not establish a sheet of water moving uniformly downwardly along the surface of the roller.
Other water dispensing or roller wetting apparatus are disclosed in U.S. Pat. Nos. 1,722,907 issued July 30, 1929 to Liddle; 2,134,883 issued Nov. 1, 1938 to Moore, Jr.; 3,109,354 issued Nov. 5, 1963 to VanKirk; 3,308,729 issued Mar. 14, 1967 to Kestel; 3,814,553 issued June 4, 1974 to Buck; 3,986,782 issued Oct. 19, 1976 to Durham; and 4,009,967 issued Mar. 1, 1977 to Layton.
The known devices have several disadvantages. None of these devices is arranged to apply a thin liquid film to a violently vibrating, inclined plate in such a way that the liquid film remains in contact with the plate. The prior arrangements for applying water to the vibratory plates of a compactor waste large quantities of water since the water is flung about in all directions by the violent cycloidal motion action of the plates, where accelerations of .+-.300 g are not uncommon.
Many objects and advantages of the present invention will be apparent to those skilled in the art from the following specification which relates to a method and apparatus for applying a thin film of a liquid to a front surface of a vibratory inclined plate of a vibratory compactor. The apparatus includes a container assembly fixed to the front surface of the inclined plate for holding a quantity of the liquid. An inlet is provided for admitting the liquid substantially uniformly to the container assembly. An element maintains intimate contact between a thin liquid film and the surface of the inclined vibratory plate of the compactor. In addition, the element reduces the flow velocity in the thin films as it starts to move downwardly by gravity and compactor acceleration along a portion of the plate within the container assembly. A thin outlet gap along substantially the entire width of the inclined plate permits the thin liquid film to flow from the container assembly as a low velocity laminar flow along the front surface of the plate in the form of a liquid sheet which remains in contact with the plate surface primarily due to surface tension.
In the preferred embodiment, the container assembly includes an elongated sheet member selectively secured generally parallel to and spaced from the surface of the inclined plate. The inlet is formed by an elongated tube having a plurality of spaced perforations along a longitudinal axis of the tube with the tube being secured to the elongated sheet member to form an upper side of the container assembly. The sheet member is preferably secured to the inclined plate by a plurality of bolts and held in spaced relation from the front surface of the plate by a plurality of spacer washers arranged between the elongated sheet member and the inclined plate. The outlet is arranged as a narrow gap formed between an edge of the elongated sheet member and the plate surface.
Further, in the preferred embodiment, the element that maintains intimate contact in open cell urethane foam rubber arranged adjacent to both the plate surface and the outlet. In a second embodiment of the present invention, the element is a serrated rubber mat arranged adjacent the inclined plate surface and a small section of foam arranged beneath the rubber mat and adjacent to the outlet of the container assembly.
The method of applying a thin film of liquid to a vibratory plate of a vibratory compactor according to the present invention includes the steps of supplying a liquid to a container assembly arranged adjacent the vibratory plate. Intimate contact is maintained between a thin liquid film and the vibratory plate surface over at least a minimum downward distance along the surface within the container assembly. The thin film is then allowed to flow downwardly from the container assembly by gravity and plate acceleration as a low velocity laminar flow along substantially the entire width of the vibratory plate in the form of a liquid sheet which remains in contact with the surface due primarily to surface tension.